I came around to it a few weeks late, but Zef and this article by Filip are also great work!

https://zef-lang.dev/implementation

https://news.ycombinator.com/item?id=47843194

It has list of more than 20 optimizations for interpreters, with measured speedups. I'm pretty sure I was looking for something like this 3-5 years ago, but it didn't exist